Function generator comprising a cam-operated leaf spring with strain gauges

ABSTRACT

The invention includes a cantilever leaf spring having strain gauges thereon. The leaf spring is bent by a cam. By using a cam of a particular configuration, the output of the strain gauges may be modified to represent any desired function of the cam angle. The leaf spring is mounted on a base which may be rotated to vary the spring deflection for a zero adjustment.

United States Patent [72] Inventors Victor Lawlord Pasadena; Richard P.Granada, Covina; Art M. D. Moen, Covina, all of Calif.

[2]] Appl. No. 832,206

[22] Filed June 11, 1969 [45] Patented Dec..7, 1971 [73] AssigneeInternational Telephone and Telegraph Corporation New York, N.Y.

FUNCTION GENERATOR COMPRISING A CAM- OPERATED LEAF SPRING WITII STRAINGAUGES 5 Claims, 3 Drawing Figs.

U.S. Cl 338/4,

. 338/36 Int. Cl. G011 1/22 Field 01 Search 235/179,

[56] References Cited UNITED STATES PATENTS 2,561,140 7/1951 Schaefer235/197 2,679,013 5/1954 Barnes 235/197 2,788,477 4/1957 MaeKay..318/20.160 UX 2,858,071 10/1958 Stokes 235/179 3,048,769 8/1962Cunningham et al... 235/197 X 3,238,532 3/1966 Michel,Jr. et 31......235/179) 2,546,155 3/1951 Haber et a1. 338/5 UX 2,992,559 7/1961 Martzet a1 235/1935 UX Primary Examiner.loseph F. Ruggiero ArlurneysC.Cornell Remsen, Jr., Walter J. Baum, Paul W. Hemminger, Percy P. Lantzyand Thomas E. Kristofi'erson ABSTRACT: The invention includes acantilever leaf spring having strain gauges thereon. The leaf spring isbent by a cam. By using a cam of a particularconfiguration, the outputof the strain gauges may be modified to represent any desired functionof the cam angle. The leaf spring is mounted on a base which may berotated to vary the spring deflection for a zero adjustment.

FUNCTION GENERATOR COMPRISING A CAM- OPERATED LEAF SPRING WITH STRAINGAUGES BACKGROUND OF THE INVENTION US Pat. No. 2,712,645. However, nosuch devices have ever 0 been used as function generators nor with anyzero adjustment.

SUMMARY OF THE INVENTION In accordance with the device of the presentinvention, the above-described and other disadvantages of the prior artare overcome by providing a cam-operated leaf spring with strain gauges.However, the cam has a configuration such that strain gauges fixedthereto provide a nonlinear output as a function of cam position.Further, a zero adjustment is provided.

The above-described and other advantages of the invention will be betterunderstood from the following description when considered in connectionwith the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing, which is to be regardedas merely illustrative:

FIG. 1 is a top plan view, partly in section, of the function generatorof the present invention;

FIG. 2 is a sectional view of the device taken on the line 2 2 shown inFIG. I; and

FIG. 3 is a schematic diagram of the strain gauge bridge.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, the output shaft of aconventional differential pressure unit is fixed to an arm 11. Rotationof arm ll with shaft 10 causes a cam 12 to rotate. Cam 12 has a pinionl3 fixed thereto. A sector gear 14 lies in mesh with pinion 13. Sectorgear 14 pivots at 15. Sector gear 14 has an arm 16 fixed thereto. Arms11 and I6 are connected by a linkage l7 pinned to arms 11 and 16 at 18and 19, respectively.

All of the structures shown in FIG. 1 are mounted on a table 20.

A base 21 is pivoted about a cap screw 22. Cap screws 23 and 24 alsohold base 21 on table 20. Base 21 has a block 25 fixed thereto. One endof cantilever leaf spring 26 is fixed to block 25 held there by a plate27 and screws 28. A free end of spring 26 has a roller 29 rotatablethereon against the surface of cam 12. Strain gauges 30 and 31 are fixedto opposite sides of spring 26.

Strain gauges 30 and 31 are connected with resistors 32 and 33 in abridge as shown in FIG. 3.

A zero adjustment is provided including a screw 23. Note will be takenin FIGS. I and 2 that base 21 has a fork portion 34 which extends arounda cam 35 fixed to screw 23, but eccentric therewith. Thus, by rotatingscrew 23, base 21 may be rotated about screw 22; and the deflection ofspring 26 may be adjusted. Base 21 has a slot 36 so that base 21 canslide under the head of screw 24.

As shown, the output of the bridge shown in FIG. 3 is proportional tothe square root of the angle through which arm l1 passes. However, bychanging the shape of the cam surface of the cam 12, the output of thebridge may be made proportional to any function of the angle throughwhich arm ll moves.

The output of the bridge of FIG. 3 is a linear function of the rise ofcam I2. However, the cam 12, itself, is nonlinear.

The rise, r, of cam 12 is where r, is the maximum rise, 0 is the anglethrough which cam l I moves, and 0,, 0 when r= r,,,.

Thus, if r,, 0.080 inches and 6,, 8, then 0 in degrees r in inches Thevalue of r, is determined by the maximum deflection which spring 26 willsafely take. 6,, preferably is 8 because a differential pressureindication is approximately linear up to 8. r,,,=0.080 inches is atypical, preferred value. Preferably, cam 12 moves through an angle of20 per l rotation of arm 1 I.

As stated previously, the curvature of cam 12 may be changed. Forexample, it may be changed to a linear, cube root or other function. Italso may be custom fit, for example, when the differential pressure unitis employed to indicate the total volume of fluid remaining in anodd-shaped tank or reservoir.

What is claimed is:

I. A function generator comprising: a cantilever leaf spring; a table; abase movable on said table; means holding one end of said spring fixedto said base; a roller rotatable at the free end of said spring; a maincam engageable with said roller; means mounted on said table to rotatesaid main cam; a strain gauge winding fixed to opposite sides of saidspring between the ends thereof; and means mounted on said table foradjusting the position of said base to vary the deflection of saidspring.

2. The invention as defined in claim I, wherein said adjustment meansincludes a cap screw having an eccentric cam therearound, said basehaving a radial fork straddling said eccentric cam, said base beingpivoted on said table at a point spaced from said screw.

3. The invention as defined in claim 2, wherein said means to rotatesaid main cam includes a sector gear, a lever fixed to said sector gear,a pinion in mesh with said sector gear, said pinion being fixed to saidmain cam, an input arm, and a linkage pinned between said arm and saidlever.

4. The invention as defined in claim 4, wherein said main cam has arise, r, given by the formula,

r,,, is the maximum rise of said main cam,

6 is the angle through which said input arm moves, and

5. A function generator comprising: a cantilever leaf spring; a table;mounting means to hold one end of said spring in a fixed positionrelative to said table; a main cam, said spring having a free endengageable with said cam; means to rotate said main cam; a strain gaugewinding fixed to at least one side of said spring between said free endthereof and said fixed end thereof, said mounting means including a basemovable on said table, said fixed spring end being fixed to said base;and means for adjusting the position of said base to vary the deflectionof said spring.

i l I! l

1. A function generator comprising: a cantilever leaf spring; a table; abase movable on said table; means holding one end of said spring fixedto said base; a roller rotatable at the free end of said spring; a maincam engageable with said roller; means mounted on said table to rotatesaid main cam; a strain gauge winding fixed to opposite sides of saidspring between the ends thereof; and means mounted on said table foradjusting the position of said base to vary the deflection of saidspring.
 2. The invention as defined in claim 1, wherein said adjustmentmeans includes a cap screw having an eccentric cam therearound, saidbase having a radial fork straddling said eccentric cam, said base beingpivoted on said table at a point spaced from said screw.
 3. Theinvention as defined in claim 2, wherein said means to rotate said maincam includes a sector gear, a lever fixed to said sector gear, a pinionin mesh with said sector gear, said pinion being fixed to said main cam,an input arm, and a linkage pinned between said arm and said lever. 4.The invention as defined in claim 4, wherein said main cam has a rise,r, given by the formula, r rm X theta / theta m where rm is the maximumrise of said main cam, theta is the angle through which said input armmoves, and theta m theta when r rm.
 5. A function generator comprising:a cantilever leaf spring; a table; mounting means to hold one end ofsaid spring in a fixed position relative to said table; a main cam, saidspring having a free end engageable with said cam; means to rotate saidmain cam; a strain gauge winding fixed to at least one side of saidspring between said free end thereof and said fixeD end thereof, saidmounting means including a base movable on said table, said fixed springend being fixed to said base; and means for adjusting the position ofsaid base to vary the deflection of said spring.